The need to make best use of limited interior space in bedrooms or to provide additional sleeping facilities in rooms not normally utilized completely as bedrooms, has prompted furniture fabricators to create a number of products which are capable of functioning as sofas or beds. Generally, such products are known as "sofa beds" and comprise multiple cushions and frame arrangements supporting the cushions by which the cushions may be configured in a position corresponding to a sofa or couch or an alternative position corresponding to a bed. A number of such products have been created through the years and have taken a wide variety of configurations and structures. However, the most common types presently employed provide a rigid frame, usually of steel members, arranged with articulated linkage configuration whereby the cushion supports, and thereby the cushions, may be arranged in alternative configurations.
By way of example, U.S. Pat. No. 4,512,048 sets forth a sofa bed which is adapted to be mounted within the interior of a automotive van. The sofa bed includes a front cushion, a rear cushion and an intermediate cushion therebetween. The cushions are pivotally mounted on a rigid steel frame which in turn is secured to the interior surfaces of the van. In the portion of the U.S. Pat. No. 4,512,048 pertinent to the present invention, the linkage is configured to allow the intermediate cushion to be pivoted between a first upright position in which it forms the seat back of a sofa and in combination with the horizontally positioned front cushion forms a bench seat and a second folded down position in which the front and intermediate cushions are aligned and horizontally positioned to form a sleeping surface in the bed configuration.
U.S. Pat. No. 4,480,344 sets fortth a divan-bed in which a frame includes a plurality of articulated leaves, each of which are covered by a continuous one-piece mattress. The end leaves on each opposite end are positioned together at an approximate right angle to form the seat and seat back of a sofa when the divan is configured in the sofa arrangement. In the sofa position, the intermediate leaves are folded into and store within the base of the divan deneath the divan seat. The structure may be reconfigured into a bed by drawing the end leaf serving as a seat portion forward. The linkage arrangement in the support structure moves the remaining segments of the support into a straight line horizontal configuration in response to the drawing force.
U.S. Pat. No. 2,721,337 sets forth a bed-davenport having essentially three cushion elements. In the sofa or davenport position, the first corresponds to the upright back portion of the sofa and the intermediate cushion drops into and is stored within the support structure. The front portion pivots so as to overlie the intermediate portion and form the bench portion of the sofa. When configured as a bed, the front portion pivots forward and away from the intermediate portion which is then raised into horizontal alignment with the pivoted front portion to form a bed surface.
U.S. Pat. No. 2,673,354 sets forth a convertible sofa bed which provides a fixed bench cushion serving as the seat bottom in the sofa position and a pivotable seat back which pivots between an upright position corresponding in the sofa configuration and a horizontal position in alignment with the fixed bench cushion to form a bed in the alternative configuration.
U.S. Pat. No. 3,310,815 sets forth a convertible sofa bunk having a pair of cushions supported by a rigid frame. In the sofa configuration, the first cushion is upright to form a seat back and the second cushion is horizontal to form a seat bench. In the alternate or bunk configuration, the second cushion slides foward to extend beyond the supporting frame of the convertible sofa bunk and the first cushion is pivoted about its upper edge to a horizontal position parallel to and raised from the second cushion. Linkage arms within the support structure latch the cushions in position to provide an offset bunk bed type arrangement.
While the sofa beds and similar devices, such as those described above, provide the advantages of dual configuration between a sofa and a bed, they are usually difficult and cumbersome to move between their two configurations. Often, the positioning and alignment of one or more of the cushions require that separate assembly be positioned and locked in place in order to provide the required support beneath a cushion in the bed configuration. Further, many of the prior art sofa bed structures provide their latching or locking function through the use of a combination of pivoting arms and spring members in which the positions of the cushions are maintained by moving the arm configurations "over-center" against the spring force. In the case of larger sofa bed units or operation by elderly persons or young children, the use of such spring force over-center structures requires an excessive or disproportionate force to reconfigure the sofa bed. As a result, the motion of the cushions and there supports between the two configurations is often difficult.
There remains therefore a need in the arm for a convertible sofa bed which utilizes a support system which provides for easy transfer between the sofa and bed configurations of the device while simultaneously providing a secure and reliable latching action in each configuration.